In vehicles that are also used for transporting persons, especially ambulances or rescue vehicles, the air, which is heated, for example, in a fuel-operated air heater, is introduced, in general, into the interior space of the vehicle at discharge sites provided in the roof area. This means that the heated air flows downward from the top. Persons standing in the interior space of the vehicle, for example, paramedics or emergency physicians in ambulances or rescue vehicles, have their heads comparatively close to these discharge sites. Since the air heated in a vehicle heater may have a temperature in the range of 80° C. and higher especially in case of heating operation with a comparatively high heat output, there is a risk that at least an unpleasant feeling may develop if the distance is short between such a discharge site and a person located in the interior space of the vehicle, but it may possibly also compromise the physical performance capacity.